Ultrathin, high-speed, all-optical photoacoustic endomicroscopy probe for guiding minimally invasive surgery

Seeing through multimode fibers using real-valued intensity transmission matrix with deep learning

Multimode fibers (MMFs) are emerging as a highly attractive technology for applications in biomedical endoscopy and telecommunications, thanks to their ability to transmit images and data through a large number of transverse optical modes. However, light transmission through MMFs suffers from distortions caused by mode dispersion and coupling. While recent deep learning advancements have shown potential for improving image transmission through MMFs, these methods typically require an extensive training dataset and often exhibit limited generalization capability. In this work, we propose a hybrid approach that combines a real-valued intensity transmission matrix (RVITM) with deep learning for enhanced image retrieval through MMFs. Our approach first characterizes the MMF and retrieves images using a RVITM algorithm, followed by refinement with a hierarchical, parallel multi-scale (HPM)-attention U-Net to improve image quality. Experimental results demonstrated that our approach achieved high-quality reconstructions, with structural similarity index (SSIM) and peak signal-to-noise ratio (PSNR) values of up to 0.9524 and 33.244 dB, respectively. This approach also offers strong generalization capabilities, requires fewer training samples and converges more quickly compared to purely deep learning-based methods reported in the literature. These results highlight the potential of our method for ultrathin endoscopy applications and spatial-mode multiplexing in telecommunications using MMFs.

Multimodal Diagnostic Imaging of Metabolic Dysfunction-Associated Steatotic Liver Disease: Noninvasive Analyses by Photoacoustic Ultrasound and Magnetic Resonance Imaging

Chronic diseases of the liver are major public health concerns worldwide. Steatosis and steatohepatitis associated with alcoholic liver disease, metabolic dysfunction-associated fatty liver disease/nonalcoholic fatty liver disease, and hepatitis B and C contribute to chronic diseases of the liver. Liver fibrosis occurs in all forms of advanced chronic diseases of the liver, the confirmation of which is typically performed by needle biopsy. Imaging approaches for liver diagnosis exist but do not provide sufficient diagnostic accuracy for defining the various stages of fibrosis or steatosis. Therefore, there is a need for improved imaging capabilities to enhance disease diagnosis. Ultrasonography-based photoacoustic imaging has recently emerged as a noninvasive, nonionizing modality, capable of capturing structural details and oxygen saturation changes during disease progression. However, its potential for detecting surrogate metabolic dysfunction-associated fatty liver disease markers, such as collagen and lipids, which are often poorly resolved by other conventional imaging techniques, has yet to be investigated in detail. The novelty of this study lies in the innovative use of spectral photoacoustic imaging for the direct detection and quantification of key biomarkers of liver disease, such as fibrosis, collagen, lipids, and oxygenated and deoxygenated hemoglobin, in a mouse model of steatotic fatty liver disease. We established that ultrasonography-based photoacoustic imaging, validated with magnetic resonance imaging, effectively identified increases in liver adiposity and fibrosis, enabling the noninvasive detection of changes in liver pathology associated with metabolic dysfunction.

Perspectives on endoscopic functional photoacoustic microscopy

Endoscopy, enabling high-resolution imaging of deep tissues and internal organs, plays an important role in basic research and clinical practice. Recent advances in photoacoustic microscopy (PAM), demonstrating excellent capabilities in high-resolution functional imaging, have sparked significant interest in its integration into the field of endoscopy. However, there are challenges in achieving functional PAM in the endoscopic setting. This Perspective article discusses current progress in the development of endoscopic PAM and the challenges related to functional measurements. Then, it points out potential directions to advance endoscopic PAM for functional imaging by leveraging fiber optics, microfabrication, optical engineering, and computational approaches. Finally, it highlights emerging opportunities for functional endoscopic PAM in basic and translational biomedicine.

Low-loss nodeless hollow-core anti-resonant soft glass fiber for the 4 µm mid-infrared spectral range

Infrared soft glass hollow-core anti-resonant fibers (HC-ARF) with low loss, excellent mode purity, and robust high-power transmission capabilities have vast potential in mid-infrared high-power laser transmission and biomedical fields. Despite this, the fabrication of these fibers still faces formidable challenges, coupled with an incomplete understanding of the transmission characteristics, thereby amplifying the value of further exploration. In this paper, we fabricate a six-cell nodeless infrared HC-ARF originating from purified sulfide glass, synthesized using a meticulous "stack-and-draw" method and dual-gas-path pressure control method. Notably, we experimentally validate the theoretical performance expectations of this fiber. The fiber exhibits outstanding transmission capabilities and optical transmission quality, characterized by a recorded loss of 0.56 dB/m at 4.79 µm. This is already comparable to traditional step-index sulfide fibers, fully demonstrating its tremendous research value and application potential. Our work has successfully fabricated the lowest loss anti-resonant fiber on record in the mid-infrared field, propelling the development of sulfide HC-ARFs into a new phase and laying a solid foundation for the realization of fiber applications in laser transmission and the biomedical field.

Photoacoustic imaging plus X: a review

Significance

Photoacoustic (PA) imaging (PAI) represents an emerging modality within the realm of biomedical imaging technology. It seamlessly blends the wealth of optical contrast with the remarkable depth of penetration offered by ultrasound. These distinctive features of PAI hold tremendous potential for various applications, including early cancer detection, functional imaging, hybrid imaging, monitoring ablation therapy, and providing guidance during surgical procedures. The synergy between PAI and other cutting-edge technologies not only enhances its capabilities but also propels it toward broader clinical applicability.

Aim

The integration of PAI with advanced technology for PA signal detection, signal processing, image reconstruction, hybrid imaging, and clinical applications has significantly bolstered the capabilities of PAI. This review endeavor contributes to a deeper comprehension of how the synergy between PAI and other advanced technologies can lead to improved applications.

Approach

An examination of the evolving research frontiers in PAI, integrated with other advanced technologies, reveals six key categories named "PAI plus X." These categories encompass a range of topics, including but not limited to PAI plus treatment, PAI plus circuits design, PAI plus accurate positioning system, PAI plus fast scanning systems, PAI plus ultrasound sensors, PAI plus advanced laser sources, PAI plus deep learning, and PAI plus other imaging modalities.

Results

After conducting a comprehensive review of the existing literature and research on PAI integrated with other technologies, various proposals have emerged to advance the development of PAI plus X. These proposals aim to enhance system hardware, improve imaging quality, and address clinical challenges effectively.

Conclusions

The progression of innovative and sophisticated approaches within each category of PAI plus X is positioned to drive significant advancements in both the development of PAI technology and its clinical applications. Furthermore, PAI not only has the potential to integrate with the above-mentioned technologies but also to broaden its applications even further.

Needle guidance with Doppler-tracked polarization-sensitive optical coherence tomography

Significance

Optical coherence tomography (OCT) can be integrated into needle probes to provide real-time navigational guidance. However, unscanned implementations, which are the simplest to build, often struggle to discriminate the relevant tissues.

Aim

We explore the use of polarization-sensitive (PS) methods as a means to enhance signal interpretability within unscanned coherence tomography probes.

Approach

Broadband light from a laser centered at 1310 nm was sent through a fiber that was embedded into a needle. The polarization signal from OCT fringes was combined with Doppler-based tracking to create visualizations of the birefringence properties of the tissue. Experiments were performed in (i) well-understood structured tissues (salmon and shrimp) and (ii) ex vivo porcine spine. The porcine experiments were selected to illustrate an epidural guidance use case.

Results

In the porcine spine, unscanned and Doppler-tracked PS OCT imaging data successfully identified the skin, subcutaneous tissue, ligament, and epidural spaces during needle insertion.

Conclusions

PS imaging within a needle probe improves signal interpretability relative to structural OCT methods and may advance the clinical utility of unscanned OCT needle probes in a variety of applications.